Are you having the laproscopic surgery --where there's a very tiny incision, they go in with tiny instruments, remove it, and you're "good to go"?
Or the more extensive cut-across-your-abdomen sort of gall bladder surgery (more "old fashioned" and out of date, but sometimes necessary)?
Any kind of surgery is a stress to the body. And sometimes -- but not always -- the stress can cause your MS symptoms to flare up.
I did have gall bladder surgery years ago -- the extensive kind -- and also had MS, and had NO complications afterwards. In fact, I got them to release me early (I wanted to go HOME!!), and I moved, and ended up having an entirely different doctor remove the stitches, some weeks later! :) (I certainly wouldn't recommend this...just the way it worked for me!!)
Do be SURE, though, to tell your doctor, your surgeon, the anesthesiologist -- EVERYONE connected to your case - -that you have MS. And be SURE to tell them ALL about any meds you are on, including prescription drugs, over-the-counter stuff, natural meds that you've picked up at the health foods store, or were given by well-meaning friends --
ANYTHING that you ingest that is not your normal food and drink. For that matter, be sure to tell them if you consume alcohol, or smoke, or do illegal drugs! All of these things will affect how the anesthegia might affect you, and might interact with your MS, so they *need to know*.
Other than that -- try to get plenty of rest before you undergo surgery, and I wish you well!
...I am not a doctor, nor health professional, and don't pretend to be one, here.....